Make sure you keep it mowed and clippings picked up. IF it is crabgrass, it is an annual from seeds. Keeping the seeds from developing and falling back to the soil will help next year. In the spring applying a good pre-em and then every 6 weeks will take care of much of the crabgrass. Most guys sorta forget to keep the pre-em down for the whole season and about this time of year start seeing break through. Gallery is my choice of pre-em with a little dimension. After the crab is seen, then it way too late. Your best choice is the old Drive, but the newer combos show to be quite effective. There's a good article on the combos in the current Turf magazine.

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